To Start my method is not what you would say is normal for freshwater. I have two 55gal setup in sync with a DIY PVC overflow leading into the other. Then from the second tank with a HOB overflow leading into a 20 gal trickel filter. I use 2 aquaeon pro 250watt heaters and a pond pump to push water into an API NEXX with 2 extensions and then back into my first tank. I have a MAXI jet 1600 in each tank to provide sufficient circulation within each tank. i believe that this is adequate but currently my tank is only 35-40% stock according to the 1 inch per gal rule my levels are zero. but i would like to put live plants and have a full tank. any input?

First, I don't think I'd push dirty water from one tank to the next - I think I'd have each dump directly into the sump and either add another pump, or a splitter for the separate returns. I'm not quite sure that I'm "seeing" how a pond pump supplies the API NEXX filter - seems like way to much pressure. In any event, why not use the 20g as a conventional sump with mechanical and bio filtration right there...perhaps augmented by the NEXX filtering water in the sump?

Note: If not already, make sure your overflows are setup to break the siphon in the event of a power outage (a hole just below the water line).